ipw2200: fix netif_*_queue() removal regression

ipw2200: fix netif_*_queue() removal regression

In "ipw2200: Call netif_*_queue() interfaces properly", netif_stop_queue()
and netif_wake_queue() were removed with the reason
"netif_carrier_{on,off}() handles starting and stopping packet flow into
the driver". The patch also removes a valid condition check that
ipw_tx_skb() cannot be called if device is not in STATUS_ASSOCIATED state.
But netif_carrier_off() doesn't guarantee netdev->hard_start_xmit won't
be called because linkwatch event is handled in a delayed workqueue. This
caused a kernel oops reported by Frank Seidel:
https://bugzilla.novell.com/show_bug.cgi?id=397390

This patch fixes the problem by moving the STATUS_ASSOCIATED check back
to ipw_tx_skb(). It also adds a missing netif_carrier_off() call to
ipw_disassociate().

Signed-off-by: Zhu Yi <yi.zhu@intel.com>
Signed-off-by: Chatre, Reinette <reinette.chatre@intel.com>
Tested-by: Frank Seidel <fseidel@suse.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>